更改嵌入式扫描仪的绿色边框（ZBar）

Question

所以我在UIViewController中有一个ZBarView（用于嵌入式扫描仪），我想知道如何更改绿色边框以使其具有这样的效果？

#import "ZBarSDK.h"

@interface ScanViewController : UIViewController <ZBarReaderViewDelegate>
@property (nonatomic, strong) IBOutlet ZBarReaderView *readerView;
@property (strong, nonatomic) IBOutlet UILabel *scannedMachineLabel;
@end


- (void)viewDidLoad
{
    [super viewDidLoad];

    _readerView.readerDelegate = self;
    // ensure initial camera orientation is correctly set
    UIApplication *app = [UIApplication sharedApplication];
    [_readerView willRotateToInterfaceOrientation: app.statusBarOrientation
                                        duration: 0];

}